1. Field of the Invention
The present invention relates to a stirring apparatus for various stirring operations, including mixing and reaction operations, for instance, stirring of a liquid-liquid system of solutions having different viscosities, stirring of a solid-liquid system of slurry-like materials and the like.
2. Description of the Prior Art
Paddle blades, turbine blades, propellor blades, multi-stage paddle blades and the like were equipped in heretofore known stirring apparatuses and used as stirring blades for stirring a fluid having a low viscosity. Helical ribbon blades, screw blades and the like were used for stirring a fluid having a high viscosity.
In the case where a liquid is fed into a stirring vessel filled with another liquid having a different viscosity, and an operation of uniformly mixing two or more kinds of liquids having different viscosities, that is, so-called hetero-viscosity mixing, is carried out by means of the above-described stirring blades in the prior art, however, the problems as described in the following are involved.
(1) If the stirring blades for low-viscosity use (paddle blades, turbine blades, propeller blades, multistage paddle blades and the like) were used, then there were problems in that the mixing performance was poor because the circulation flows of the material to be stirred within a stirring vessel were formed only in the proximity of the stirring blades and circulation flows over the entire space within the vessel could not be formed. Also the power efficiency was poor, because the stirring power has consumed only in the proximity of the stirring blades. PA1 (2) If the stirring blades for high-viscosity use (helical ribbon blades, screw blades and the like) were used, then there were problems in that although the blades revealed an excellent mixing performance for high-viscosity liquids (liquids having a viscosity of several hundreds to several thousands poise or higher), circulation flows over the entire space within the vessel could not be formed for relatively low-viscosity liquids (liquids having a viscosity of several thousands to several hundreds poise or lower), and so the mixing performance was poor. In addition, these types of stirring blades had shortcomings that manufacture was difficult and high in costs and cleaning at the time of stoppage of an operation was not easy because the configurations of the blades were complicated. PA1 (1) ascending flows are generated in the material to be processed in the proximity of the inner wall surface of the stirring vessel by the upper action of the vertical flat blade, the first and second inclined flat blades and the first and second vertical flat blades that are each associated with a sweptback blade; PA1 (2) descending flows are generated in the material to be processed in the proximity of the center axis of the stirring vessel by the action of the inclined flat blades; and PA1 (3) as a result of the above-mentioned phenomena (1) and (2), circulation flows are formed over the entire region within the stirring vessel.